Solid-phase crystal growth of molecular-beam-deposited amorphous GaAs

Abstract

Solid-phase crystallization processes of molecular-beam-deposited amorphous GaAs with various As/Ga composition ratios are investigated by reflection high-energy electron diffraction, Rutherford backscattering spectroscopies, and time-resolved reflectivity measurements at various annealing temperatures. In a low-temperature region (≲300 °C), solid-phase epitaxial growth takes place, and the activation energy of the growth rate (1.6 eV) is shown to agree well with that of the ion-implanted amorphized GaAs. In a high-temperature region (≳400 °C), polycrystallization takes place, followed by a realignment of the polycrystal to a single crystal. The epitaxial growth rate is more strongly affected by the As/Ga composition ratio for the low-temperature crystallization than for the high-temperature crystallization. The interface roughnesses between crystallized and amorphous layers are evaluated to be 14–20 nm from the reflectivity measurements and the transmission electron microscopy. The atomic bonding state in the amorphous GaAs is examined by Auger electron spectroscopy, and no local precipitation of As atoms is detected in the nearly stoichiometric film.